1. Field of the Invention
The present invention relates to an apparatus and a method for extracting artificial image such as a telop from an input image signal and a program for performing the method. Particularly, it relates to an apparatus and the like for extracting pixel data corresponding to the artificial image from the input image signal whose each piece of the pixel data is constituted of multiple items of color data.
2. Description of Related Art
In TV broadcasting, a moving telop (characters) has used to display a news flash and the like on a screen. If pixel data corresponding to an artificial image including such a telop is extracted from an image signal, it is possible to utilize this pixel data by, for example, accumulating it in a hard disk drive (HDD).
Conventionally, an apparatus has been proposed which extracts pixel data corresponding to a telop from an image signal (see Japanese Patent Application Publication No. 2000-182053). In this case, by utilizing telop properties of high luminance and color saturation with respect to a background, an edge position of a telop is detected on the basis of luminance and color saturation values. An average and a variance of luminance and color saturation values of a telop region including this edge position are then obtained, so that based on these average and variance, pixel data corresponding to the telop is extracted from an image signal.
Thus, the conventional apparatus detects an edge position of the telop based on luminance and color saturation values. It, however, cannot accurately detect the edge position of the telop on a level of the luminance and color saturation values. It is feared that only pixel data corresponding to the telop cannot be extracted from an image signal properly.
It is an object of the present invention to provide an apparatus and the like for extracting only pixel data corresponding to an artificial image properly from an input image signal.